Camera having distance measuring apparatus

ABSTRACT

A camera having a distance measuring apparatus according to the present invention includes a photo receiving unit receiving object images focused by photo-receiving lenses; a selecting unit selecting any one of distance-measuring area in a photographing plane; and a determining unit determining whether or not an extreme value exists in outputs from the photo receiving unit, in the distance-measuring area selected by the selecting unit. When the determining unit determines that no extreme value exists, the selecting unit selects a second distance-measuring area having outputs whose inclination orientation is opposite to that of the outputs from the photo receiving unit, in the initially-selected first distance-measuring area.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims benefits of Japanese ApplicationsNo. 2002-358297 in Japan on Dec. 10, 2002, No. 2002-358298 filed inJapan on Dec. 10, 2002, No. 2003-402273 filed in Japan on Dec. 1, 2003,No. 2003-402274 filed in Japan on Dec. 1, 2003, the contents of whichare incorporated by this reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a camera having a distance measuringapparatus and more particularly, it relates to a camera having adistance measuring apparatus having a multi-autofocus function withwhich ranges of a plurality of areas in a photographing plane are found.

[0004] 2. Related Art Statement

[0005] As is widely known, there are two autofocus (hereinafter, calledAF) types used for the distance measuring of a camera: one is a “passivetype” in which an AF sensor disposed in the main body of a cameradirectly receives an image signal (optical image), the other is an“active type” in which a camera projects distance measuring fill lighttoward an object and receives its reflected light.

[0006] Also, even in a passive AF camera, when an object lies in a darkplace or the contrast of an object is low, fill light is projected forlighting up the object or for making the variations of brightness anddarkness larger on the object, so that a process of an active type isperformed so as to improve distance measuring accuracy.

[0007] In addition, a technique with which a fixed-light removingfunction for removing a component of light reflected at an object otherthan the fill light or distance measuring light (hereinafter, thecomponent is called fixed light) is provided so as to improve detectingaccuracy of the reflected light has been also known and disclosed inJapanese Unexamined Patent Application Publication No. 5-40037.

[0008] An object of the present invention is to provide a camera havinga distance measuring apparatus which prevents an out-of-focus picture bycorrecting an influence of fill light reflected at the surface of a lensbarrel or at a highly reflective component disposed in the vicinity ofthe AF sensor when a certain picture-taking scene requires fill light tobe illuminated.

BRIEF SUMMARY OF THE INVENTION

[0009] Briefly speaking, a camera having a distance measuring apparatuswhich performs distance measuring of a plurality of distance measuringareas in a photographing plane, according to the present invention,includes a photo-receiving lens, each forming an object image; a photoreceiving unit receiving the object image formed by the photo-receivinglens; a computing unit computing data about object-to-camera distanceson the plurality of distance measuring areas on the basis of outputs ofthe photo receiving unit; a selecting unit selecting any one of thedistance measuring areas in the photographing plane on the basis of thecomputed results of the computing unit; and a determining unitdetermining whether or not an extreme value exists in outputs of thephoto receiving unit, in the distance measuring area selected by theselecting unit, and when the determining unit determines that theextreme value does not exist, the selecting unit selects a seconddistance measuring area different from the initially-selected firstdistance measuring area.

[0010] Additional features and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Thefeatures and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram illustrating the general structure of anentire electrical circuit of a camera having a distance measuringapparatus according to a first embodiment of the present invention;

[0012]FIG. 2A is an electrical circuit diagram illustrating thestructure of a fixed-light removing unit of the camera according to thefirst embodiment;

[0013]FIG. 2B is a timing chart of the fixed-light removing unit of thecamera according to the first embodiment;

[0014]FIG. 3A is a schematic view of an AF distance-measuring range ateach zoom position of the camera according to the first embodiment;

[0015]FIG. 3B is a diagram illustrating the relationship between AFdistance-measuring range and focal distance at each zoom position of thecamera according to the first embodiment;

[0016]FIG. 4 is a schematic view of a major part of the camera accordingto the first embodiment, illustrating incident light for distancemeasuring;

[0017]FIG. 5A is a diagram illustrating a phenomenon that stroboscopiclight flashed by an electronic flash unit of the camera according to thefirst embodiment toward an object has an influence on the AF sensor;

[0018]FIG. 5B is a diagram illustrating the phenomenon that stroboscopiclight flashed by the electronic flash unit of the camera according tothe first embodiment toward an object has an influence on the AF sensor;

[0019]FIG. 5C is a diagram illustrating the phenomenon that stroboscopiclight flashed by the electronic flash unit of the camera according tothe first embodiment toward an object has an influence on the AF sensor;

[0020]FIG. 6A is a diagram illustrating a method for preventing adistance longer or shorter than an actual distance from being computedwhen output values of sensor data have no extreme value;

[0021]FIG. 6B is a diagram illustrating the method for preventing adistance longer or shorter than an actual distance from being computedwhen the output values of the sensor data have no extreme value;

[0022]FIG. 7 is a flowchart illustrating a distance-measuring control(AF control) by a CPU of the camera according to the first embodiment;

[0023]FIG. 8A is a flowchart illustrating a pre-integration control ofthe camera according to the first embodiment in a passive mode;

[0024]FIG. 8B is a timing chart illustrating the pre-integration controlof the camera according to the first embodiment in a passive mode;

[0025]FIG. 9A is a flowchart illustrating an integration control of thecamera according to the first embodiment in an active mode;

[0026]FIG. 9B is a timing chart illustrating the integration control ofthe camera according to the first embodiment in an active mode;

[0027]FIG. 10A is a flowchart illustrating an integration control of thecamera according to the first embodiment when it is determined that apicture-taking scene is in a middle-level brightness or high-levelbrightness condition;

[0028]FIG. 10B is a timing chart illustrating the integration control ofthe camera according to the first embodiment when it is determined thatthe picture-taking scene is in a middle-level brightness or high-levelbrightness condition;

[0029]FIG. 11 is a flowchart illustrating a setting control of adistance-measuring range by the AF sensor of the camera according to thefirst embodiment;

[0030]FIG. 12 is a flowchart illustrating a control of a 1/L averagingprocess of the camera according to the first embodiment; and

[0031]FIG. 13 is a block diagram illustrating an electrical circuit of amodification of the camera having a distance measuring apparatusaccording to the first embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] First of all, a first embodiment will be described.

[0033]FIG. 1 is a block diagram illustrating the general structure of anelectrical circuit of a camera having a distance measuring apparatusaccording to the first embodiment of the present invention.

[0034] The camera is an autofocus camera and also has a zoom mechanismfor changing a focal distance of its photographing optical system.

[0035] As shown in FIG. 1, the camera having a distance measuringapparatus has an arithmetic control circuit (hereinafter, called CPU) 1disposed therein, constituted of an one-chip microcomputer and the like,for controlling an overall operational sequence of the camera inaccordance with a switching operation by an operator. Connected to theCPU 1 are a stroboscope 5 a having an electronic flash unit 5 forflashing stroboscopic light toward an object; an integration determiningunit 6; a release switch 8 for starting a shooting sequence of thecamera; a focusing unit 9 controlling a focusing operation of thephotographing optical system (not shown); an A/D converting unit(converter) 16 converting integrated outputs of image signals from apair of sensor arrays 3 a and 3 b, which will be described later, intodigital signals; and a zoom-position detecting unit 17.

[0036] Also, the pair of sensor arrays 3 a and 3 b have a fixed-lightremoving unit 7 connected to the output terminals thereof, and thefixed-light removing unit 7 has the integration determining unit 6 andthe A/D converting unit 16 connected to the output terminals thereof.The pair of sensor arrays 3 a and 3 b are respectively formed by asensor array containing juxtaposing pixels used for photo receptors andconstitutes an AF sensor 3 which is disposed so as to face an object 21of which distance is measured and which has a pair of photo-receivinglenses 2 a and 2 b and an integration circuit (not shown).

[0037] The CPU 1 has an EEPROM 4 serving as a nonvolatile storage forstoring parameters needed for controlling a camera operation and anoperating state of the camera, a control unit 10 responsible forcontrolling the entire camera, a pattern determining unit 11, acorrelation computing unit 12, a reliability determining unit 13, and alight-quantity determining unit 14. The pattern determining unit 11 isconnected to the control unit 10 and reliability determining unit 13,the reliability determining unit 13 is connected to the control unit 10and the correlation computing unit 12, the control unit 10 is connectedto the EEPROM 4, and the EEPROM 4 is connected to the light-quantitydetermining unit 14.

[0038] The AF sensor 3 detects a camera-to-object distance L extendingfrom the camera to the object 21. Images of the object 21 obtainedthrough a pair of the photo-receiving lenses 2 a and 2 b disposed awayfrom each other by a base length (parallax) B are formed on the pair ofsensor arrays 3 a and 3 b disposed at a position of a focal distance f,and the camera-to-object distance L is detected by the CPU 1 on thebasis of a difference x in image positions with respect to the parallaxby using the known triangulation principle.

[0039] Relative positions, with respect to the optical axes of thephoto-receiving lenses 2 a and 2 b, of the images of the object 21formed on the pair of sensor arrays 3 a and 3 b vary in accordance withthe magnitude of the camera-to-object distance L detected as describedabove.

[0040] In order to detect the relative positions, the A/D convertingunit 16 converts integrated outputs (here, an integration circuit isincluded in each pixel of the sensor arrays 3 a and 3b) constitutingimage signals of the object from the sensor arrays 3 a and 3 b, intodigital signals and outputs them to the CPU 1. The CPU 1 comparesdigital image signals of the sensor array 3 a and 3 b outputted from theA/D converting unit 16 to each other so that the relative positionaldifference and camera-to-object distance are detected.

[0041] With the above comparison by the CPU 1, the digital image signalsdetected by the pair of sensor arrays 3 a and 3 b are checked whether ornot these signals are generated from the same object 21. In the CPU 1,the pattern determining unit 11 determines whether or not patterns ofthe digital image signals are appropriate for distance measuring, andthe correlation computing unit 12 detects a relative positionaldifference of images from the digital image signals.

[0042] On the basis of the coincidence level of the images upondetecting the relative positions or on the basis of results of patterndetermination of the images, if the images have low contrast, repetitivepatterns, monotonously increasing patterns, or monotonously decreasingpatterns, the reliability determining unit 13 determines thatreliability of the distance measuring is low. Also, when removing fixedlight, the electronic flash unit 5 projects distance-measuring lightonto the object 21 so as to be reflected thereat so that thelight-quantity determining unit 14 determines quantities of lightincident on the pair of sensor arrays 3 a and 3 b.

[0043] The focusing unit 9 decides a control amount of a focusingoperation of the photographing optical system on the basis of thesedetermined results in the CPU 1. Also, the CPU 1 determines a variety ofcamera manipulations, such as a turn-on operation of the release switch8 performed by an operator, in order to control a picture-takingoperation, and in addition, also when distance-measuring, the CPU 1controls the stroboscope 5 a if needed so as to cause the electronicflash unit 5 to flash light appropriately.

[0044] Meanwhile, the integration determining unit 6 determines whetheror not the integral values reach predetermined values on the basis ofthe integrated outputs from the pair of sensor arrays 3 a and 3 b.

[0045] In the event of the distance measuring, the fixed-light removingunit 7 removes a light component originating in fixed light such assunlight or artificial illumination illuminating an object. Outputs ofthe fixed-light removing unit 7 and the light-quantity determining unit14 determining the brightness of an object are compared with a constantread out from the EEPROM 4, and a pulse width of distance-measuringlight during the distance measuring is determined in accordance with themagnitudes of the constant. Also, the fixed-light removing unit 7determines the brightness of the object on the basis of the outputresults of the sensor arrays 3 a and 3 b when projecting thedistance-measuring light.

[0046] Next, a circuit constituting the fixed-light removing unit 7,formed in association with each of the pixels constituting, for example,the sensor array 3 a shown in the FIG. 1, and its operation will bedescribed. FIG. 2A is an electrical circuit diagram illustrating thestructure and a timing chart of the fixed-light removing unit 7.

[0047] As shown in FIG. 2A, in the fixed-light removing unit 7, a serialcircuit formed by the sensor array 3 a and a fixed-light removingtransistor 7 a and a holding capacitor 7 b are connected to a currentdetecting circuit 7 c, and the output terminal of the current detectingcircuit 7 c is connected to an integration amplifier 18 a having a resetswitch 18 d interposed therebetween. An integration circuit 18 is formedby the integration amplifier 18 a and a parallel circuit formed by anintegration capacitor 18 b and a reset switch 18 c, both connectedbetween the output and input terminals of the amplifier 18 a.

[0048] A photoelectric current Ip outputted from the sensor array 3 a ispassed to a GND (ground) via the fixed-light removing transistor 7 a inaccordance with the quantity of light incident on the sensor array 3 a.In this state, the current detecting circuit 7 c controls a gate voltageof the fixed-light removing transistor 7 a so as to prevent a currentfrom passing through the integration circuit 18 formed by theintegration amplifier 18 a, the integration capacitor 18 b, the resetswitches 18 c and 18 d, and the like.

[0049] The holding capacitor 7 b is disposed so as to fix the gatevoltage at a certain value. In this fixed state, for example, when thestroboscope 5 a causes the electronic flash unit 5 to flash light so asto project distance-measuring light in a pulsed manner toward the object21 (see FIG. 1), and also the current detecting circuit 7 c is set in anon-operative mode, the voltage across both ends of the holdingcapacitor 7 b is irresponsive to a sharp pulsed change of thedistance-measuring light. In this state, when the reset switch 18 d isbeing turned on, only the photoelectric current Ip in accordance withthe pulse light is inputted into the integration circuit 18, and thus aphotoelectric conversion voltage based on the distance-measuring lightis outputted from the output terminal of the integration amplifier 18 a.Thus, when this output is subjected to A/D conversion, data of aquantity of reflected light in accordance with reflected signal light isdetected.

[0050] Also, in order to determine whether a picture-taking scene isbright or dark, the current detecting circuit 7 c is set in anon-operative mode. Then, as shown in FIG. 2B, after the reset switch 18c is temporarily turned on, the fixed-light current Ip is passed intothe integration circuit 18, and an integrated voltage Vc integrated fora predetermined time period tINT is measured and is stored in the EEPROM4 (see FIG. 1). With this arrangement, since Vc is generally low in abright scene and high in a dark scene, a bright/dark determination canbe made by measuring the level of the integrated voltage Vc.

[0051]FIG. 3A illustrates an AF distance-measuring range varying inconjunction with a focal distance of a taking lens.

[0052] As shown in FIG. 3A, an angle of field of the taking lens (notshown) is generally widened (TELE→WIDE) as the focal distance decreases(comes closer to the wide angle side). In this state, when an angle ofAF view of each of the photo-receiving lenses 2 a and 2 b (see FIG. 1)remains constant, since the ratio of the angle of AF view to the angleof field of the taking lens decreases, an object lying in the peripheryof the photographing plane of the taking lens falls out of focus.

[0053] To prevent the above problem, the camera having a distancemeasuring apparatus according to the present embodiment has a structurein which, in order to keep the ratio of a distance-measuring angle to anangle of picture field constant in accordance with the detected resultof the focal distance of the zoom-position detecting unit 17 (see FIG.1), the distance-measuring range is changed in three steps of A, B, andC by using information concerning the focal distance stored in theEEPROM 4 (see FIG. 1) such that the number of pixels to be effective,serving as photo receptors of the pair of sensor arrays 3 a and 3 bincrease as the focal distance comes closer to the wide angle side.

[0054]FIG. 3B shows the information concerning the focal distance storedin the EEPROM 4, illustrating a manner of changing thedistance-measuring ranges by using the relationship between focaldistance and AF distance-measuring range.

[0055] As described above, even when the focal distance is changed bythe zoom mechanism, and the angle of picture field is thus widened, theratio of the distance-measuring angle to the angle of picture field canbe kept constant by changing the AF distance-measuring range inconjunction with the focal distance.

[0056] Next, a phenomenon that stroboscopic light flashed by theelectronic flash unit 5 toward the object has an influence on the AFsensor 3 will be described with reference to a schematic view of a majorpart of the camera in FIG. 4 and diagrams in FIGS. 5A to 5C.

[0057] As shown in FIG. 4, the camera having a distance measuringapparatus 100 according to the present invention has the electronicflash unit 5, a front panel 20, a taking lens barrel 22, the pair ofphoto-receiving lenses 2 a and 2 b, and the pair of sensor arrays 3 aand 3 b, and as shown in FIG. 1, the fixed-light removing unit 7, theA/D conversion unit 16, and so forth are connected to the pair of sensorarrays 3 a and 3 b.

[0058] In the camera having the above-described structure, when filllight is projected from the electronic flash unit 5 so as to measure adistance to the object 21, by converting integrated outputs from thesensor arrays 3 a and 3 b into digital signals by the A/D convertingunit 16, image signals as shown in FIG. 5A are generally obtained. Then,when their correlations are computed by the correlation computing unit12 (see FIG. 1), a relative positional difference of images is computed,and the camera-to-object distance L is thus computed.

[0059] However, when the stroboscope is flashed, for example, as shownin FIG. 4, a part of stroboscopic light from the electronic flash unit 5is reflected at the surface of the lens barrel 22 and is incident on theend surface of the front panel 20, and its fixed light incident on theend surface of the front panel 20 is diffusively reflected thereat andglistens in a flare-like manner, thereby being incident on the sensorarray 3 a.

[0060] In such a case, as shown in FIG. 5B, a difference in integrationlevels of an image signal 3 a′ outputted from the sensor array 3 a onwhich the above light is incident and an image signal 3 b′ outputtedfrom the sensor array 3 b on which the above light is not incident isgenerated, resulting that only the sensor array 3 a is influenced by thephenomenon that the front panel 20 is glistening in a flare-like manner.

[0061] A difference in the integration levels can be corrected, forexample, by computing a difference in average values of respective allsensor data of the sensor arrays 3 a and 3 b. However, when the frontpanel 20 glistens in a flare-like manner, the sensor data is sometimesdeformed as shown in FIG. 5C. In that case, even when its correlation iscomputed by the correlation computing unit 12, the computed correlationmay result in a wrong one.

[0062] The reason of this is explained as follows. In the case shown inFIG. 5A, the correlation results of all Δa1, Δa2, and Δa3 are unchanged.However, in the case shown in FIG. 5C, although the correlation resultof Δc2 serving as an extreme value is the same as that of Δa2, Δa1 andΔc1 have a relationship of Δa1 >Δc1, thereby resulting in computing alonger distance than the actual camera-to-object distance L in the caseshown in FIG. 5C, and also Δa3 and Δc3 have a relationship of Δa1 <Δc3,thereby resulting in computing a shorter distance than the actualcamera-to-object distance L in the case shown in FIG. 5C.

[0063] Each of the diagrams in FIGS. 5A to 5C illustrates sensor dataobtained when distance measuring is performed in a typicalpicture-taking scene where fill light is effective, and to be morespecific, for example, a scene where there is a figure with a backgroundof a night scene is assumed.

[0064] In such a picture-taking scene, the reason why the sensor data asshown in FIG. 5A is obtained, as described above, is such that lightcoming from the night scene is removed as fixed light by the fixed-lightremoving unit 7 (see FIG. 1), and only data coming from fill lightflashed from the electronic flash unit 5, which is reflected at thefigure and is then incident on the pair of sensor arrays 3 a and 3 b, isreflected in the sensor data.

[0065] Meanwhile, also in the case of FIG. 5B, although the fill lightreflected at the lens barrel 22 (see FIG. 4) is incident on the sensorarray 3 a as shown in FIG. 4, the reason why the sensor data in thiscase is not the same as that shown in FIG. 5A is such that, since lightglistening in a flare-like manner on the front panel 20 is incident onthe sensor array 3 a as described above, the light has an influence onthe sensor data of the sensor array 3 a, thereby causing an integrationof the sensor data of the sensor array 3 a to be advanced as a whole.

[0066] Next, when no extreme value exists in a range used for computinga distance of the sensor data, a method for preventing computing adistance longer or shorter than an actual distance as shown in FIG. 5Cwill be described with reference to a diagram in FIG. 6A.

[0067] This method is achieved by utilizing a feature as follows: In thecase where the sensor data of the sensor array 3 a is deformed (itsintegration is advanced as a whole) due to the flare-like glistening ofthe front panel 20 (see FIG. 4) as shown in the FIG. 5C, further if noextreme value exists in a selected distance-measuring area and itsdistance-measured result is shifted to the long distance side,distance-measured results in another distance-measuring area having noextreme value and whose inclination orientation is opposite to that ofthe selected distance-measuring area whose distance-measured result isshifted to the long distance side is shifted to the short distance side.

[0068] To be more specific, as shown in FIG. 6A, an integration of thewhole sensor data of the sensor array 3 a is advanced due to aninfluence of the above-described fill light concerning the sensor datashown in FIG. 6A, when the reciprocal 1/L (1) of its distance iscomputed by computing its correlation with respect to the selecteddistance-measuring area, it is shifted to the long distance side if nocorrection is applied.

[0069] With this having in mind, in the case where, for example, 20sensors are used in the selected distance-measuring area as shown inFIG. 6B, an average value Ave;n (n=1, 2, 3, 4) of the sensor data ofevery 5 sensors is computed, and in addition, a difference ΔAve;m (m=1,2, 3) between two of the average values is computed. When all values ofΔAve;m are negative, it is found that the sensor data of the selecteddistance-measuring area has no extreme value and the distance-measuredvalue decreases.

[0070] Then, a distance-measuring area having sensor data whoseinclination orientation is opposite to that of the sensor data of theselected distance-measuring area is searched for. In the same fashion asin the selected distance-measuring area, an average value Ave;n′ (n′=1,2, 3, 4) of the sensor data of every 5 sensors is computed, and adifference ΔAve;m′ (m′=1, 2, 3) between two of the average values iscomputed. When all values of ΔAve;m′ are positive, it is determined thatthe sensor data in the searched distance-measuring area has an oppositeinclination orientation.

[0071] With this arrangement, the reciprocals 1/L (2) of the searcheddistance-measuring area having the opposite inclination orientation iscomputed, and then, an average value of the 1/L (1) and 1/L (2) iscomputed, so that the distance-measured result is prevented from beingshifted to the long distance side.

[0072] Meanwhile, when there is a plurality of distance-measuring areashaving an opposite inclination orientation, the distance-measuring areaclosest to the selected distance-measuring area having an extreme valuetherebetween is selected. Also, concerning the searching direction ofthe distance-measuring areas having an opposite inclination orientation,an extreme value is searched for in the direction along which a sensornumber becomes larger or smaller when all ΔAve;m are negative orpositive, respectively.

[0073] Next, a correcting-operation control of the CPU 1 in the casewhere digital values outputted from the sensor arrays 3 a and 3 b andtransformed are influenced by fill light reflected at the surface of thelens barrel 22, and hence a level difference of the digital values isgenerated between the sensor arrays, will be described with reference toflowcharts in FIG. 7 and other figures.

[0074] Meanwhile, a mode in which distance measuring is performed byusing a relative positional difference of image signals of an object ofwhich distance is measured without projection of distance-measuring filllight is called “passive mode”, and a mode in which distance measuringis performed by using a relative positional difference of image signalsof an object of which distance is measured with removal of the fixedlight and with projection of distance-measuring fill light such asstroboscopic light is called “active mode”.

[0075]FIG. 7 is a main flowchart illustrating a distance-measuringcontrol (AF control) of the CPU 1.

[0076] As shown in FIG. 7, first of all, in Step S1, distance measuringis performed in the passive mode without projecting distance-measuringfill light, a pre-integration is then executed with the pair of sensorarrays 3 a and 3 b for a given time period, and the process moves toStep S2.

[0077] In Step S2, it is determined whether a picture-taking scene is ina low-level brightness or high-level brightness condition in accordancewith a degree of advancement of the pre-integration executed in Step S1.When the picture-taking scene is in a low-level brightness condition,the process moves to Step S3, and when the picture-taking scene is in ahigh-level brightness condition, the process branches to Step S9.

[0078] When the picture-taking scene is in a low-level brightnesscondition, in Step S3, a distance-measuring area of an object is set inconjunction with its focal distance (see FIGS. 3A and 11), and theprocess moves to Step S4. In Step S4, the distance measuring isperformed in the active mode in which the distance measuring isperformed with projection of the above-described distance-measuring filllight, a first distance-measuring area is selected (see FIG. 9A), andthe process moves to Step S5.

[0079] It is determined in Step S5 whether or not the distance measuringperformed in the active mode in the Step S4 is succeeded. Here, thephrase “distance measuring is succeeded” is defined such that acorrelation and an interpolation are computed by the correlationcomputing unit 12 (see FIG. 1), which is a known technology, amisaligned between images of the pair of sensor arrays 3 a and 3 b iscomputed on the basis of these results, and the known reliabilitydetermination whether or not the misaligned amount between the images isright is performed by the reliability determining unit 13. When thedistance measuring in the active mode is succeeded, the process moves toStep S7. When failed, the process branches to Step S6, the distancemeasuring is performed with an AF computation of a quantity of reflectedlight, and then the distance measuring is finished. Such a rangingsystem is a distance measuring system utilizing a phenomenon that, whenlight is projected and a quantity of its reflected light is measured, alarge quantity of light is reflected at an object close to a camera, anda small quantity of light is reflected at an object far away from thecamera, and this system is effective for a very-low-contrast object,although it is assumed that the reflectance of the object lies in apredetermined range.

[0080] When the distance measuring is succeeded, it is determined inStep S7 whether or not the number of fill-light flashing times is notless than a predetermined number of times or a difference in averagevalues of sensor data from the pair of sensor arrays 3 a and 3 b is notless than a predetermined value. When either one is not less than thecorresponding predetermined value, the process moves to Step S8. In StepS8, a second distance-measuring area having an inclination orientationopposite to that in the first distance-measuring area selected in StepS4 is searched for, 1/L (2) of the searched distance-measuring areahaving the opposite inclination orientation is computed, theabove-described 1/L averaging process (see FIGS. 6A and 12) of computingan average value of 1/L (1) of the first distance-measuring areaselected in Step S4 and 1/L (2) of the second distance-measuring areahaving the opposite inclination orientation is conducted, and thedistance measuring is finished. When both are less than thecorresponding predetermined values, the process branches to Step S18,1/L of the distance-measuring areas is computed in Step S18 with theknown closest selection, and the distance measuring is finished.

[0081] In the meantime, the reason why only the condition that thenumber of fill-light flashing times is not less than a predeterminednumber of times is set in Step S7 is such that, when the number offill-light flashing times is small, a small number of times ofreflection from the above-described lens barrel decreases and also noisedecreases. Also, the reason why the averaging process, which will bedescribed later, is performed only when a difference in the averagevalues of the sensor data from the sensor arrays 3 a and 3 b is not lessthan the predetermined value, when the difference in the average valuesof the sensor data of the pair of sensor arrays 3 a and 3 b is small, itcan be determined that the fill light reflected at the lens barrel has asmall influence. However, when a further accurate control is required,the condition in Step S7 allowing the process to move to Step S8 ischanged to that in which the number of fill-light flashing times is notless than the predetermined number of times and also the difference inthe average values of the sensor data from the pair of sensor arrays 3 aand 3 b is not less than the predetermined value.

[0082] Back to Step S2, when the picture-taking scene is in a high-levelbrightness condition, the process branches to Step S9, adistance-measuring area of the object is set, and the process moves toStep S10. In step S10, the distance measuring is performed in thepassive mode, and the process moves to Step S11.

[0083] It is determined in Step S11 whether or not the distancemeasuring performed in the passive mode is succeeded. When the distancemeasuring is succeeded, the distance measuring is finished. When failed,the process branches to Step S12.

[0084] In Step S12, a distance-measuring area of the object is setagain, and the process moves to Step S13. In Step S13, the distancemeasuring is performed again in the active mode, and the process movesto Step S14.

[0085] It is determined in Step S14 whether or not the distancemeasuring performed in the active mode in the Step S13 is succeeded.When the distance measuring performed in the active mode is succeeded,the process moves to Step S15. When failed, the process branches to StepS17, an AF computation of a quantity of reflected light is performed,and then the distance measuring is finished.

[0086] When the distance measuring is succeeded, it is determined inStep S15 whether or not the number of fill-light flashing times is notless than the predetermined number of times or the difference in theaverage values of the sensor data from the pair of sensor arrays 3 a and3 b is not less than the predetermined value. When either one is notless than the corresponding predetermined value, the process moves toStep S16, the above-described 1/L averaging process is conducted, andthe distance measuring is finished. When both are less than thecorresponding predetermined values, the process branches to Step S19,1/L of the distance-measuring area is computed in Step S19 with theknown closest selection, and the distance measuring is finished.

[0087] Next, a control of the pre-integration in the passive mode shownin the Step S1 will be described with reference to a flowchart of asubroutine in FIG. 8A.

[0088] As shown in FIG. 8A, first of all, an integration is executed inStep S30 for the predetermined time period tINT. The integration isstarted after the resetting switch 18 c (see FIG. 2A) is temporarilyturned on as shown in FIG. 8B. In this state, an integrated voltage VINTduring the integration is detected for the predetermined time periodtINT and is stored in the EEPROM 4 (see FIG. 1) or the like. Then theprocess moves to Step S31.

[0089] Meanwhile, since the integrated voltage VINT is generally low ina bright picture-taking scene and high in a dark picture-taking scene, abright/dark determination of an object can be performed by detecting theintegrated voltage VINT.

[0090] Thus, in Step S31, it is determined whether the integratedvoltage VINT obtained by the integration during the period of tINT inthe Step S30 is higher or lower than a low-level brightnessdetermination voltage Vth serving as a threshold for determining whetheror not the picture-taking scene is in a low-level brightness condition.When the integrated voltage VINT is higher than the low-level brightnessdetermination voltage Vth, the process moves to Step S32, it isdetermined that the scene is in a low-level brightness condition, andthe pre-integration is finished. When the integrated voltage VINT islower than the low-level brightness determination voltage Vth, theprocess moves to Step S33, it is determined that the scene is in amiddle-level brightness or high-level brightness condition, and thepre-integration is finished.

[0091] Next, a control of the integration in the active mode shown inthe Steps S4 and S13 will be described with reference to a flowchart ofa subroutine in FIG. 9A.

[0092] As shown in FIG. 9A, first of all, in Step S40, anintegration-counting variable n is cleared, and the process moves toStep S41. Then, in Steps S41 to S45, as shown in FIG. 9B, the fill lightis flashed for a predetermined time period until the integrated voltageVINT reaches a predetermined voltage Vang, and the integration byflashing is repeated.

[0093] The number of sensor arrays involved for outputting theintegrated voltage VINT may be all of them or may be determined inaccordance with a value stored in the EEPROM 4 (see FIG. 1). Inaddition, an integrated voltage of a sensor having the largest or thesmallest quantity of incident light among sensors involved foroutputting the integrated voltage may be selected as the integratedvoltage VINT.

[0094] Also, generally the number of sensor arrays involved foroutputting the integrated voltage VINT is often only one of the pair ofsensor arrays since power consumption of the EEPROM 4 can be curbed, andalso a control for setting sensor arrays to be involved can besimplified. However, in the case where the integrated voltage of onlyone of the pair of sensor arrays is selected to be outputted, if filllight has an influence on the sensor array whose sensors are notselected for outputting the integrated voltage, as shown in theabove-described FIG. 6A, an A/D value of the sensor array which is notselected is sometimes saturated. In such a case, even if the A/D valuelevel of the sensor array is corrected, since the level of coincidenceof images is low, a relative phase difference varies, thereby resultingin an inaccurate distance-measured result.

[0095] Hence, the integration-finish voltage Vang in the active mode isset higher than an integration-finish voltage Vpng (see FIG. 1OB) in thepassive mode so as to prevent the A/D value from being saturated evenwhen the fill light has an influence on the sensor array.

[0096] It is determined in Step S42 whether or not the integratedvoltage VINT reaches the integration-finish voltage Vang. When theintegrated voltage VINT reaches the integration-finish voltage Vang, theprocess moves to Step S45, and the integration is finished. Then, theprocess moves to Step S46.

[0097] When the integrated voltage VINT does not reach theintegration-finish voltage Vang, the process branches to Step S43, andit is determined whether or not the number of integration times reachesthe predetermined number of times. If the number of integration timesreaches the predetermined number of times, the process moves to StepS45. If not reaching the predetermined number of times, the processmoves to Step S41, and Steps S41 to S44 are repeated until reaching theintegration-finish voltage Vang. The integration by flashing executedmore than the predetermined number of times causes a waste of energy andhas an influence on a time lag of a distance-measuring operation and thelike, whereby a limiter is set in Step S44 at an appropriate number ofintegration times.

[0098] In Step S46, a pattern determination is performed by thereliability determining unit 13 (see FIG. 1) taking reflected light intoconsideration, and the process moves to Step S47. It is determined inStep 847 whether or not triangulation is possible on the basis of thedetermined result in Step S46. When an image signal is atriangulation-possible reflected-light image signal, the process movesto Step S48, and the triangulation is performed. In the subsequent StepS49, the closest selection for selecting a distance-measuring areaoutputting the closest distance-measured result among a plurality ofdistance-measuring areas is performed, and the integration in the activemode is finished.

[0099] Back to Step S47, when it is determined that the triangulation isimpossible, the process moves to Step S50, a distance-measuring failuredetermination is made, and the integration in the active mode isfinished.

[0100] Next, concerning the pre-integration in the passive mode shown inFIG. 8A, an integration control in the case where it is determined thatthe picture-taking scene is in a middle-level brightness or high-levelbrightness condition will be described with reference to a flowchart ofa subroutine in FIG. 10A.

[0101] As shown in FIG. 10A, first of all, in Step S51, a timer (notshown) disposed in the CPU 1 (see FIG. 1) is started in order to measurean integration time. Since an excessively long integration time causes arelease time lag and a risk that an operator misses picture-takingtiming, in general, the integration time is given by a specifiedintegration limit-time. That is, when the integration time exceeds theintegration limit-time, the integration in the passive mode is finishedat once. The integration limit-time is stored in the EEPROM 4 or thelike. After the timer is started in Step S51, the process moves to StepS52.

[0102] In Step S52, as shown in FIG. 1OB, after the reset switch 18 c(see FIG. 1) is temporarily turned on, the integration is started, andthe process moves to Step S53.

[0103] It is determined in Step S53 whether or not the time tINTmeasured by the timer exceeds an integration limit-time tlim or whetheror not the integrated voltage VINT becomes lower than theintegration-finish voltage Vpng stored in the EEPROM 4 or the like. Theintegration is executed until the tINT exceeds the integrationlimit-time tlim or the integrated voltage VINT becomes lower than theintegration-finish voltage Vpng, and then the process moves to Step S54.

[0104] In the case where the integration is further continued even whenthe integrated voltage VINT becomes lower than the integration-finishvoltage Vpng, the integrated voltage becomes saturated in the end,thereby making an image signal of the object and signals around theobject indistinguishable from each other and resulting in inaccuratedistance measuring. Accordingly, the integration is finished in StepS54, and the process moves to Step S55. In step S55, the timer formeasuring an integration time is stopped, and the process moves to StepS56.

[0105] It is determined in Step S56 whether or not the integratedvoltage VINT still remains higher than the integration-finish voltageVpng even when the integration time exceeds the integration limit-timetlim. When the integrated voltage VINT is higher than theintegration-finish voltage Vpng, since a triangulation-possible imagesignal is not obtained, the process branches to Step S57, thedistance-measuring failure determination is made, and the integration inthe passive mode is finished.

[0106] Back to Step S56, when the integrated voltage VINT becomes lowerthan the integration-finish voltage Vpng after the integration timeexceeds the integration limit-time tlim, the process moves to Step S58,and the triangulation is performed. Then, in the subsequent Step S59,the closest selection for selecting a distance-measuring area outputtingthe closest distance-measured result among the plurality ofdistance-measuring areas is performed, and the integration in thepassive mode is finished.

[0107] Next, a control of setting the distance-measuring range by the AFsensor 3 shown in Step S3 in FIGS. 3A, 3B, and 7 is described withreference to a flowchart of a subroutine in FIG. 11.

[0108] As shown in FIG. 11, first of all, in Step S60, a present zoomposition is determined on the basis of a detected result by the zoomposition detecting unit 17 (see FIG. 1). When it is determined that thepresent zoom position lies in the vicinity of TELE, the process moves toStep S61, and the distance-measuring range A (see FIGS. 3A and 3B) isselected. Also, when it is determined that the present zoom positionlies in the vicinity of STANDARD, the process moves to Step S62, and thedistance-measuring range B (see FIGS. 3A and 3B) is selected. Inaddition, when it is determined that the present zoom position lies inthe vicinity of WIDE, the process jumps to Step S63, and thedistance-measuring range C (see FIGS. 3A and 3B) is selected.

[0109] Subsequently, the 1/L averaging process shown in Step S8 in FIGS.6A, 6B, and 7 will be described with reference to a flowchart of asubroutine in FIG. 12.

[0110] As shown in FIG. 12, first of all, it is determined in Step S12whether or not the sensor data of the selected distance-measuring areahas an extreme value. With an extreme value, the process moves to StepS71, the 1/L is computed, and then the process returns. Without anextreme value, the process branches to Step S72.

[0111] In Step S72, a-distance-measuring area having sensor data whoseinclination orientation is opposite to that of the sensor data in theselected distance-measuring area is searched for, and the process movesto Step S73. In Step S73, 1/L of the selected distance-measuring areaand 1/L of the searched distance-measuring area whose inclinationorientation is opposite to that of the selected distance-measuring areaare computed, and the process moves to Step S74. Also, in Step S74, anaverage value of the two 1/Ls computed in Step S73 is computed, and thenthe process returns.

[0112] As described above, in the camera having a distance measuringapparatus according to the first embodiment, in the case where apicture-taking scene is a night scene or the like and when illuminationof fill light is necessary in the event of performing AF distancemeasuring, an influence of the fill light reflected at the surface ofthe lens barrel 22 or at a highly reflective component disposed in thevicinity of the AF sensor 3 is curbed such that an area is selectedamong a plurality of distance-measuring areas for obtaining adistance-measured result, another area having sensor data whoseinclination orientation is opposite to that of sensor data of theselected area, having an extreme value interposed therebetween, issearched for, and an average value of the reciprocals of distances ofthe selected area and the searched area having the opposite inclinationorientation is computed.

[0113] When the above control is performed, the influence of the filllight reflected at the surface of the lens barrel 22 or at a highlyreflective component disposed in the vicinity of the AF sensor 3 isprevented from causing an inaccurate distance-measured result and thusleading to an out-of-focus picture.

[0114] Although, the camera having a distance measuring apparatusoperable in two kinds of distance-measuring modes of the active andpassive modes is exemplified in the first embodiment, even with adistance measuring in a modification shown in FIG. 13, which does nothave the fixed-light removing unit 7, the influence of the fill lightcan be curbed in the same fashion as in the above-described embodimentsuch that an area is selected among a plurality of distance-measuringareas for obtaining a distance-measured result, another area havingsensor data whose inclination orientation is opposite to that of sensordata of the selected area, having an extreme value interposedtherebetween, is searched for, and an average value of the reciprocalsof distances of the selected area and the searched area having theopposite inclination orientation is computed.

[0115] Next, a second embodiment of the present invention will bedescribed.

[0116] Since a camera having a distance measuring apparatus according tothe second embodiment of the present invention basically has the samestructure as in the first embodiment, only different parts will bedescribed below.

[0117] In both first and second embodiments of the present invention,when no extreme value exists in a range used for computing a distance ofsensor data, a second distance-measuring area different from aninitially-selected first distance-measuring area is selected.

[0118] In particular, the present embodiment is achieved by utilizing afeature as follows: In the case where the sensor data of the sensorarray 3 a is deformed (its integration is advanced as a whole) due tothe flare-like glistening of the front panel 20 (see FIG. 4) as shown inFIG. 5C, further if no extreme value exists in a selecteddistance-measuring area and its distance-measured results are shifted tothe long distance side, distance-measured results in anotherdistance-measuring area having no extreme value and whose inclinationorientation is opposite to that of the selected distance-measuring areawhose distance-measured result is shifted to the long distance side areshifted to the short distance side.

[0119] To be more specific, as shown in FIG. 6A, an integration of thewhole sensor data of the sensor array 3 a is advanced due to aninfluence of the above-described fill light. Concerning the sensor datashown in FIG. 6A, when the reciprocal 1/L (1) of its distance iscomputed by computing its correlation with respect to the selecteddistance-measuring area, it is shifted to the long distance side if nocorrection is applied.

[0120] Hence, according to the second embodiment, distance-measuredresults are prevented from being shifted to the long distance side bythe following method.

[0121] That is, a distance-measuring area having sensor data whoseaverage value is closest to that of other sensor data of a selecteddistance-measuring area is searched for, and 1/L (2) of the searcheddistance-measuring area having the sensor data whose average value isclosest to that of the other sensor data of the distance-measuring areais computed. By computing an average value of the 1/L (1) and 1/L (2) asdescribed above, the distance-measured results are prevented from beingshifted to the long distance side. Meanwhile, the distance-measuringarea having the sensor data whose average value is closest to the othersensor data of the selected distance-measuring area is searched fortoward a minimal value.

[0122] Also, the 1/L averaging process in Step S8 shown in FIG. 7 in thesecond embodiment is different from that in the first embodiment. Aprocess down to the 1/L averaging process will be described below withreference to FIG. 7.

[0123] In the second embodiment, in the same fashion as in the firstembodiment, it is determined in Step S5 whether or not the distancemeasuring performed in the active mode in Step S4 is succeeded. When thedistance measuring in the active mode is succeeded, the process moves toStep S7. When failed, the process branches to Step S6, the distancemeasuring is performed with an AF computation of a quantity of reflectedlight, and then the distance measuring is finished. When the distancemeasuring is succeeded, in the second embodiment, it is determined inStep S7 whether or not the number of fill-light flashing times is notless than a predetermined number of times or a difference in the averagevalues of the sensor data of the pair of sensor arrays 3 a and 3 b isnot less than a predetermined value. When either one is not less thanthe corresponding predetermined value, the process moves to Step S8. InStep S8, a second distance-measuring area having sensor data whoseaverage value is closest to that of the sensor data in the firstdistance-measuring area selected in Step S4 is searched for, 1/L (2) ofthe searched distance-measuring area is computed, the above-described1/L averaging process (see FIGS. 6A and 12) of computing an averagevalue of 1/L (1) of the first distance-measuring area selected in StepS4 and 1/L (2) of the second distance-measuring area is conducted, andthe distance measuring is finished. When both are less than thecorresponding predetermined values, the process branches to Step S18,1/L of the distance-measuring areas is computed in Step S18 with theknown closest selection, and the distance measuring is finished.

[0124] Since other operations in the second embodiment are the same asthose in the first embodiment, their description is omitted.

[0125] Meanwhile, other embodiments formed by, for example, combiningparts of the above-described embodiments fall in the scope of thepresent invention.

[0126] In this invention, it is apparent that working modes different ina wide range can be formed on this basis of this invention withoutdeparting from the spirit and scope of the invention. This invention isnot restricted by any specific embodiment except being limited by theappended claims.

What is claimed is:
 1. A camera having a distance measuring apparatus which performs distance measuring of a plurality of distance-measuring areas in a photographing plane, comprising: photo-receiving lenses, each forming an object image; a photo receiving unit receiving the object images formed by the photo-receiving lenses; a computing unit computing data about object-to-camera distances on the plurality of distance-measuring areas on the basis of outputs of the photo receiving unit; a selecting unit selecting any one of the distance-measuring areas in the photographing plane on the basis of the computed results of the computing unit; and a determining unit determining whether or not an extreme value exists in outputs of the photo receiving unit, in the distance-measuring area selected by the selecting unit, wherein, when the determining unit determines that the extreme value does not exist, the selecting unit selects a second distance-measuring area different from the initially-selected first distance-measuring area.
 2. The camera having a distance measuring apparatus according to claim 1, wherein the selecting unit selects a second distance-measuring area having outputs whose inclination orientation is opposite to that of the outputs from the photo receiving unit in the initially-selected first distance-measuring area.
 3. The camera having a distance measuring apparatus according to claim 1, wherein the selecting unit selects a second distance-measuring area having the average value of the outputs in the initially-selected first distance-measuring area.
 4. A camera having a distance measuring apparatus which performs distance measuring of a plurality of distance-measuring areas in a photographing plane, comprising: photo-receiving lenses, each forming an object image; a photo receiving unit receiving the object images formed by the photo-receiving lenses; a computing unit computing data about object-to-camera distances of the plurality of distance-measuring areas on the basis of outputs of the photo receiving unit; a selecting unit selecting any one of the distance-measuring areas in the photographing plane on the basis of the computed results of the computing unit; a determining unit determining whether or not an extreme value exists in outputs of the photo receiving unit, in the distance-measuring area selected by the selecting unit, and a focusing unit adjusting the focus of a photographing optical system, wherein, when the determining unit determines that the extreme value does not exist, the selecting unit selects a second distance-measuring area having outputs whose inclination orientation is opposite to that of the outputs from the photo receiving unit in the initially-selected first distance-measuring area.
 5. The camera having a distance measuring apparatus according to claim 4, wherein the computing unit computes an average value of the data about camera-to-object distances in the first and second distance-measuring areas selected by the selecting unit.
 6. The camera having a distance measuring apparatus according to claim 5, further comprising a projecting unit projecting a light beam toward an object, wherein the computing unit computes the average value when the number of projecting times of the projecting unit is not less than a predetermined number of times.
 7. The camera having a distance measuring apparatus according to claim 6, wherein the photo receiving unit constitutes a pair of line sensors, and wherein, when a difference in average values of outputs of the pair of line sensors is not less than a predetermined value, the computing unit computes the average values.
 8. The camera having a distance measuring apparatus according to claim 5, wherein the focusing unit adjusts the focus of the photographing optical system on the basis of the average value.
 9. The camera having a distance measuring apparatus according to claim 4, wherein, in the event where the selecting unit selects the second distance-measuring area, when there is a plurality of outputs, having the opposite inclination orientation, from the photo receiving unit, a distance-measuring area which has outputs having the opposite inclination orientation and which lies closest to the first distance-measuring area is selected.
 10. The camera having a distance measuring apparatus according to claim 4, further comprising a searching unit searching for outputs whose inclination orientation is opposite to that of the outputs from the photo receiving unit in the first distance-measuring area, wherein the searching unit preferentially searches, from the photo receiving unit, for outputs in a distance-measuring area lying in a direction along which the extreme value exists, when viewed from the first distance-measuring area.
 11. The camera having a distance measuring apparatus according to claim 6, further comprising a brightness-determining unit determining whether or not at least a part of the region in the photographing plane is in a low-level brightness condition, on the basis of outputs from the receiving unit when the projecting unit is in a non-projecting mode.
 12. The camera having a distance measuring apparatus according to claim 11, wherein, when the brightness determining unit determines that the part of the region is in a low-level brightness condition, the projecting unit projects a light beam toward an object.
 13. The camera having a distance measuring apparatus according to claim 11, wherein, when the brightness determining unit determines that the part of the region is in a high-level brightness condition, distance measuring is performed with a light beam not being projected by the projecting unit.
 14. The camera having a distance measuring apparatus according to claim 6, wherein the projecting unit flashes stroboscopic light toward an object.
 15. A camera having a distance measuring apparatus which performs distance measuring of a plurality of distance-measuring areas in a photographing plane, comprising: photo-receiving lenses, each forming an object image; a photo receiving unit receiving the object images formed by the photo-receiving lenses; a computing unit computing data about object-to-camera distances in the plurality of distance-measuring areas on the basis of outputs of the photo receiving unit; a selecting unit selecting any one of the distance-measuring areas in the photographing plane on the basis of the computed results of the computing unit; a determining unit determining whether or not an extreme value exists in outputs of the photo receiving unit, in the distance-measuring area selected by the selecting unit, and a focusing unit adjusting the focus of a photographing optical system, wherein, when the determining unit determines that the extreme value does not exist, the selecting unit selects a second distance-measuring area having outputs whose average value is closest to that of the outputs from the photo receiving unit in the initially-selected first distance-measuring area.
 16. The camera having a distance measuring apparatus according to claim 15, wherein the computing unit computes an average value of data about object-to-camera distances in the first and second distance-measuring areas selected by the selecting unit.
 17. The camera having a distance measuring apparatus according to claim 16, further comprising a projecting unit projecting a light beam toward an object, wherein, when the number of projecting times of the projecting unit is not less than a predetermined number of times, the computing unit computes the average value.
 18. The camera having a distance measuring apparatus according to claim 16, wherein the photo receiving unit constitutes a pair of line sensors, and wherein, when a difference in average values of outputs of the pair of line sensors is not less than a predetermined value, the computing unit computes the average values.
 19. The camera having a distance measuring apparatus according to claim 16, wherein the focusing unit adjusts the focus of the photographing optical system on the basis of the average value.
 20. The camera having a distance measuring apparatus according to claim 15, wherein, in the event where the selecting unit selects the second distance-measuring area, when there is a plurality of outputs having the opposite inclination orientation, from the photo receiving unit, a distance-measuring area which has outputs having the opposite inclination orientation and which lies closest to the first distance-measuring area is selected.
 21. The camera having a distance measuring apparatus according to claim 15, further comprising a searching unit searching for outputs whose inclination orientation is opposite to that of the outputs from the photo receiving unit in the first distance-measuring area, wherein the searching unit preferentially searches, from the photo receiving unit, for outputs in a distance-measuring area lying in a direction along which the extreme value exist, when viewed from the first distance-measuring area.
 22. The camera having a distance measuring apparatus according to claim 17, further comprising a brightness-determining unit determining whether or not at least a part of the region in the photographing plane is in a low-level brightness condition, on the basis of outputs from the receiving unit when the projecting unit is in a non-projecting mode.
 23. The camera having a distance measuring apparatus according to claim 22, wherein, when the brightness determining unit determines that the part of the region is in a low-level brightness condition, the projecting unit projects a light beam toward an object.
 24. The camera having a distance measuring apparatus according to claim 22, wherein, when the brightness determining unit determines that the part of the region is in a high-level brightness condition, distance measuring is performed with a light beam not being projected by the projecting unit.
 25. The camera having a distance measuring apparatus according to claim 17, wherein the projecting unit flashes stroboscopic light toward an object. 